The present invention relates to inserts for cutting tools, and more particularly to serrated triangular cutting tool inserts of the type adapted to be detachably inserted in a holder.
Conventional cutting tools often have straight cutting edges. It has been found that the energy needed to operate cutting tools can be reduced by having interruptions in the cutting edge so that one blade or insert of a cutter does not completely cut through the stock presented to it. A second insert following the first in the cutting tool, will remove the stock not removed by the first cutting insert. Inserts of this type generally have four similar cutting edges, and these cutting edges must be indexed by marking the edges differently to ensure correct arrangement in the cutting tool.
United Kingdom Pat. No. 1,237,538 (U.S. Pat. No. 3,636,602) describes cutting inserts of various geometrical shapes having cutting edges in which recesses extend transversely along the edge face from the side face. The recesses on each edge face are asymmetrically disposed about the center of the face so that each recess on one side of the face is paired with a land on the other side of the face. To ensure proper wiping of the stock being cut, the inserts must be carefully arranged in the cutter such that first one cutting edge is presented to the stock and then the opposing cutting edge is presented in the adjacent insert. The inserts of U.K. Pat. No. 1,237,538 may have an out-of-phase relationship of the cutting edges when mounted at spaced-apart locations on a holder to reduce power consumption and heat generated, however it is desirable to further reduce these factors.
In United Kingdom Pat. No. 1,537,177, a cutting insert which is polygonal in shape and has two parallel faces connected by peripheral walls is described. There are spaced parallel grooves between the cutting edges. The number of grooves on one side is different from the number of grooves on an adjacent side.
United Kingdom Pat. Application No. 2,008,008A describes an insert having parallel faces with peripheral walls, and in the peripheral walls recesses interrupt the cutting edges.
United Kingdom Pat. No. 2,054,427 describes an assembly having a detachable positive rake insert for a cutting tool having three or more contiguous edge faces of equal length and two side faces each edge face having one or more recesses which extend across the whole of the edge face and which extend transversely or substantially transversely to the cutting edge formed where each edge face meets one of the side faces of the blade, the recesses being spaced apart to leave a plurality of coplanar lands, the number of recesses on any two adjacent edge faces being different, the recess at the cutting edge having a width which is the same as or less than the width of the intervening lands at the cutting edge, which recess increases in width as it extends away from its cutting edge. This insert operates entirely satisfactorily but is difficult to index when the insert has other than four edges. The inserts described in United Kingdom Pat. No. 1,237,538 function because they have 90.degree. angles between edge faces and side faces (negative rake inserts) which makes it possible to index the inserts correctly by using both side faces to achieve recess overlapping.
The inserts described in United Kingdom Patent No. 2,054,427 function because they are single sided in operation (positive rake) with the angle between the top face and any side face being less than 90.degree.. Indexing is achieved in this case due to pairs of faces having different numbers of recesses.
Indexing becomes a particular problem when a positive rake triangular insert is used, and it is desirable to overcome this problem. Furthermore, it is desirable to improve inserts so that there is a reduction or avoidance of shock and a reduction in power consumption and heat generated.